George Monbiot rightly observes that the earth's resources of biomass are limited and cannot be simultaneously claimed for multiple uses: liquid biofuels, fuel for heating, biogas, and biochar. This presentation (available for download in PowerPoint or PDF) looks at the globe's land and biomass production to assess how much space can be given over to non-food uses and how much energy this can generate. This is one of the crucial questions facing the world: how much energy can we use from biomass before this affects the ability of the world to provide enough food for nearly 7bn people, rising to at least 9bn by 2050?